From: Yu Kuai <yukuai1@huaweicloud.com>
To: Greg KH <gregkh@linuxfoundation.org>, Yu Kuai <yukuai1@huaweicloud.com>
Cc: hch@infradead.org, ming.lei@redhat.com, axboe@kernel.dk,
roger.pau@citrix.com, colyli@suse.de, kent.overstreet@gmail.com,
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yi.zhang@huawei.com, yangerkun@huawei.com,
"yukuai (C)" <yukuai3@huawei.com>
Subject: Re: [PATCH -next] block: remove field 'bd_inode' from block_device
Date: Mon, 27 Nov 2023 09:13:39 +0800 [thread overview]
Message-ID: <6ef798a6-8c0c-16b0-9991-b461258eb7d4@huaweicloud.com> (raw)
In-Reply-To: <2023112544-subpanel-national-58e5@gregkh>
Hi,
在 2023/11/25 22:32, Greg KH 写道:
> On Sat, Nov 25, 2023 at 05:39:12PM +0800, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> block_devcie is allocated from bdev_alloc() by bdev_alloc_inode(), and
>> currently block_device contains a pointer that point to the address of
>> inode, while such inode is allocated together:
>>
>> bdev_alloc
>> inode = new_inode()
>> // inode is &bdev_inode->vfs_inode
>> bdev = I_BDEV(inode)
>> // bdev is &bdev_inode->bdev
>> bdev->inode = inode
>>
>> Add a new helper to get address of inode from bdev by add operation
>> instead of memory access, which is more efficiency. Also prepare to
>> add a new field 'bd_flags' in the first cacheline(64 bytes).
>>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>> ---
>> block/bdev.c | 39 +++++++++++++++++-------------
>> block/blk-zoned.c | 4 +--
>> block/fops.c | 4 +--
>> block/genhd.c | 8 +++---
>> block/ioctl.c | 8 +++---
>> block/partitions/core.c | 9 ++++---
>> drivers/block/xen-blkback/xenbus.c | 2 +-
>> drivers/md/bcache/super.c | 2 +-
>> drivers/mtd/devices/block2mtd.c | 12 ++++-----
>> drivers/s390/block/dasd_ioctl.c | 2 +-
>> drivers/scsi/scsicam.c | 2 +-
>> fs/bcachefs/util.h | 2 +-
>> fs/btrfs/disk-io.c | 6 ++---
>> fs/btrfs/volumes.c | 4 +--
>> fs/btrfs/zoned.c | 2 +-
>> fs/buffer.c | 8 +++---
>> fs/cramfs/inode.c | 2 +-
>> fs/erofs/data.c | 2 +-
>> fs/ext4/dir.c | 2 +-
>> fs/ext4/ext4_jbd2.c | 2 +-
>> fs/ext4/super.c | 8 +++---
>> fs/gfs2/glock.c | 2 +-
>> fs/gfs2/ops_fstype.c | 2 +-
>> fs/jbd2/journal.c | 3 ++-
>> fs/jbd2/recovery.c | 2 +-
>> fs/nilfs2/segment.c | 2 +-
>> include/linux/blk_types.h | 10 ++++++--
>> include/linux/blkdev.h | 4 +--
>> include/linux/buffer_head.h | 4 +--
>> 29 files changed, 86 insertions(+), 73 deletions(-)
>
> You should do this as a patch series, add the helper function that does
> nothing, convert all the different portions of the kernel as different
> patches, and _then_ change the implementation of the block layer to
> handle the change in the structure.
>
> Otherwise this is going to be hard to get accepted.
Okay, thanks for the adivce, I'll do that in v2.
By the way, I was thinking that this patch is quite simple, and doesn't
worth spliting into 10+ patches,
>
> Also, one note:
>
>> @@ -85,6 +84,13 @@ struct block_device {
>> #define bdev_kobj(_bdev) \
>> (&((_bdev)->bd_device.kobj))
>>
>> +static inline struct inode *bdev_inode(struct block_device *bdev)
>> +{
>> + void *inode = bdev + 1;
>
> That's crazy, if something changes, this will keep working yet the
> kernel will break and no one will know why.
>
> Please use container_of(), that's what it is there for, this exact type
> of thing. Or if not, are you just assuming that the memory location
> right after bdev is the inode? That's a tough assumption, how are you
> going to assure it really stays there?
Struct bdev_inode never changes since commit 8fbd544cbca5 ("[PATCH]
bdev: add I_BDEV()") from 2004, and I think it won't change unless
there is a different way to manage lifetime of block_device.
And the 'bdev + 1' is copied from blk_mq_rq_to_pdu(), however, I aggre
that use container_of() is better and I will use it in v2.
Thanks,
Kuai
>
> thanks,
>
> greg k-h
> .
>
prev parent reply other threads:[~2023-11-27 1:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-25 9:39 [PATCH -next] block: remove field 'bd_inode' from block_device Yu Kuai
2023-11-25 14:32 ` Greg KH
2023-11-27 1:13 ` Yu Kuai [this message]
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